The 30 day rule
Wait 30 days before making a purchase to have a better perspective if the item is valuable and avoid urge buying.
Make a Shopping List
Shop only when you have a list to save money and get rid of impulse buying.
Drink More Water
The only drink with great health and financial benefits. It will make your body properly hydrated and make you spend less on beverages like pop or juice.
The 10 Second Rule
Before you put the item in your cart, STOP for 10 second. Ask yourself "Why do I need to buy this?" and "Do I actually need this?". If there is no reasonable answer, then put them back.. you don't need it!
Avoid Convenience Foods
Goods at convenience store are expensive, you might want to consider preparing healthy snacks and meals for your trip and save money instead.
Source: The Simple Dollar